The present invention relates to an improved process for the preparation of certain epothilone analogs.
Epothilones are macrolide compounds that find utility in the pharmaceutical field. For example, epothilones A and B having the structures: 
may be found to exert microtubule-stabilizing effects similar to paclitaxel (TAXOL(copyright)) and hence cytotoxic activity against rapidly proliferating cells, such as, tumor cells or other hyperproliferative cellular disease, see Hofle, G., et al., Angew. Chem. Int. Ed. Engl., Vol. 35, No.13/14, 1567-1569 (1996); WO93/10121 published May 27, 1993; and WO97/19086 published May 29, 1997.
Derivatives and analogs of epothilones A and B have been synthesized and may be used to treat a variety of cancers and other abnormal proliferative diseases. Such analogs are disclosed in Hofle et al., Id.; Nicolaou, K. C., et al., Angew. Chem. Int. Ed. Engl. Vol. 36, No. 19, 2097-2103 (1997); and Su, D. -S., et al., Angew. Chem. Int. Ed. Engl. Vol. 36, No. 19, 2093-2097 (1997).
The present invention is directed to a process for the preparation of compounds represented by formulas I and II wherein X, P1, P2, R1 and R2 are as defined below: 
The compounds represented by formulas I and II are intermediates for the preparation of epothilone analogs that are useful in the treatment of a variety of cancers and other abnormal proliferative diseases.
The process of the present invention provides an advantageous synthesis for the compounds represented by formulas I and II 
Compounds of formula I can be utilized to prepare, for example, analogs represented by formula II which can, in turn, be utilized to prepare epothilone analogs represented by the formulas III and IV. 
As used in the formulas I, II, III, IV and throughout the specification, the symbols as given below have the following meanings:
X is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl and substituted aryl;
R1 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, and heterocyclo;
R2 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, heterocyclo or 
R3 and R4 are selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl and heterocyclo;
P1, P2, P3 are independently selected from the group consisting of hydrogen, aralkyl, substituted aralkyl, trialkylsilyl, triarylsilyl, dialkylarylsilyl, diarylalkylsilylalkoxyalkyl, and aralkyloxyalkyl.
Definitions
The following are definitions of various terms used herein to describe this invention. These definitions apply to the terms as they are used throughout this specification, unless otherwise limited in specific instances, either individually or as part of a larger group.
The term xe2x80x9calkylxe2x80x9d refers to optionally substituted straight- or branched-chain saturated hydrocarbon groups having from 1 to 20 carbon atoms, preferably from 1 to 7 carbon atoms. The expression xe2x80x9clower alkylxe2x80x9d refers to optionally substituted alkyl groups having from 1 to 4 carbon atoms.
The term xe2x80x9csubstituted alkylxe2x80x9d refers to an alkyl group substituted by, for example, one to four substituents, such as, halo, trifluoromethyl, trifluoromethoxy, hydroxy, alkoxy, cycloalkyoxy, heterocylooxy, oxo, alkanoyl, aryl, aryloxy, aralkyl, alkanoyloxy, amino, alkylamino, arylamino, aralkylamino, cycloalkylamino, heterocycloamino, disubstituted amino in which the two substituents on the amino group are selected from alkyl, aryl, aralkyl, alkanoylamino, aroylamino, aralkanoylamino, substituted alkanoylamino, substituted arylamino, substituted aralkanoylamino, thiol, alkylthio, arylthio, aralkylthio, cycloalkylthio, heterocyclothio, alkylthiono, arylthiono, aralkylthiono, alkylsulfonyl, arylsulfonyl, aralkylsulfonyl, sulfonamido (e.g. SO2NH2), substituted sulfonamido, nitro, cyano, carboxy, carbamyl (e.g. CONH2), substituted carbamyl (e.g. CONH alkyl, CONH aryl, CONH aralkyl or instances where there are two substituents on the nitrogen selected from alkyl, aryl or aralkyl), alkoxycarbonyl, aryl, substituted aryl, guanidino and heterocyclos, such as, indolyl, imidazolyl, furyl, thienyl, thiazolyl, pyrrolidyl, pyridyl, pyrimidyl and the like. Wherein, as noted above, the substituents themselves are further substituted, such further substituents are selected from the group consisting of halogen, alkyl, alkoxy, aryl and aralkyl. The definitions given herein for alkyl and substituted alkyl apply as well to the alkyl portion of alkoxy groups.
The term xe2x80x9chalogenxe2x80x9d or xe2x80x9chaloxe2x80x9d refers to fluorine, chlorine, bromine and iodine.
The term xe2x80x9carylxe2x80x9d refers to monocyclic or bicyclic aromatic hydrocarbon groups having from 6 to 12 carbon atoms in the ring portion, for example, phenyl, naphthyl, biphenyl and diphenyl groups, each of which may be substituted.
The term xe2x80x9caralkylxe2x80x9d refers to an aryl group bonded to a larger entity through an alkyl group, such as benzyl.
The term xe2x80x9csubstituted arylxe2x80x9d refers to an aryl group substituted by, for example, one to four substituents such as alkyl; substituted alkyl, halo, trifluoromethyl, trifluoromethoxy, hydroxy, alkoxy, cycloalkyloxy, heterocyclooxy, alkanoyl, alkanoyloxy, amino, alkylamino, dialkylamino, aralkylamino, cycloalkylamino, heterocycloamino, alkanoylamino, thiol, alkylthio, cycloalkylthio, heterocyclothio, ureido, nitro, cyano, carboxy, carboxyalkyl, carbamyl, alkoxycarbonyl, alkylthiono, arylthiono, alkysulfonyl, sulfonamido, aryloxy and the like. The substituent may be further substituted by one or more members selected from the group consisting of halo, hydroxy, alkyl, alkoxy, aryl, substituted alkyl, substituted aryl and aralkyl.
The term xe2x80x9ccycloalkylxe2x80x9d refers to optionally substituted saturated cyclic hydrocarbon ring systems, preferably containing 1 to 3 rings and 3 to 7 carbons per ring, which may be further fused with an unsaturated C3-C7 carbocyclic ring. Exemplary groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, cyclododecyl, and adamantyl. Exemplary substituents include one or more alkyl groups as described above, or one or more of the groups described above as substituents for alkyl groups.
The terms xe2x80x9cheterocyclexe2x80x9d, xe2x80x9cheterocyclicxe2x80x9d and xe2x80x9cheterocycloxe2x80x9d refer to an optionally substituted, unsaturated, partially saturated, or fully saturated, aromatic or nonaromatic cyclic group, for example, which is a 4 to 7 membered monocyclic, 7 to 11 membered bicyclic, or 10 to 15 membered tricyclic ring system, which has at least one heteroatom in at least one carbon atom-containing ring. Each ring of the heterocyclic group containing a heteroatom may have 1, 2 or 3 heteroatoms selected from nitrogen atoms, oxygen atoms and sulfur atoms, where the nitrogen and sulfur heteroatoms may also optionally be oxidized and the nitrogen heteroatoms may also optionally be quaternized. The heterocyclic group may be attached at any heteroatom or carbon atom.
Exemplary monocyclic heterocyclic groups include pyrrolidinyl, pyrrolyl, indolyl, pyrazolyl, oxetanyl, pyrazolinyl, imidazolyl, imidazolinyl, imidazolidinyl, oxazolyl, oxazolidinyl, isoxazolinyl, isoxazolyl, thiazolyl, thiadiazolyl, thiazolidinyl, isothiazolyl, isothiazolidinyl, furyl, tetrahydrofuryl, thienyl, oxadiazolyl, piperidinyl, piperazinyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, 2-oxazepinyl, azepinyl, 4-piperidonyl, pyridyl, N-oxo-pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, tetrahydropyranyl, tetrahydrothiopyranyl, tetrahydrothiopyranyl sulfone, morpholinyl, thiomorpholinyl, thiomorpholinyl sulfoxide, thiomorpholinyl sulfone, 1,3-dioxolane and tetrahydro-1, 1-dioxothienyl, dioxanyl, isothiazolidinyl, thietanyl, thiiranyl, triazinyl, and triazolyl, and the like.
Exemplary bicyclic heterocyclic groups include benzothiazolyl, benzoxazolyl, benzothienyl, quinuclidinyl, quinolinyl, quinolinyl-N-oxide, tetrahydroisoquinolinyl, isoquinolinyl, benzimidazolyl, benzopyranyl, indolizinyl, benzofuryl, chromonyl, coumarinyl, cinnolinyl, quinoxalinyl, indazolyl, pyrrolopyridyl, furopyridinyl (such as furo[2,3-c]pyridinyl, furo[3,1-b]pyridinyl] or furo[2,3-b]pyridinyl), dihydroisoindolyl, dihydroquinazolinyl (such as 3,4-dihydro-4-oxo-quinazolinyl), benzisothiazolyl, benzisoxazolyl, benzodiazinyl, benzofurazanyl, benzothiopyranyl, benzotriazolyl, benzpyrazolyl, dihydrobenzofuryl, dihydrobenzothienyl, dihydrobenzothiopyranyl, dihydrobenzothiopyranyl sulfone, dihydrobenzopyranyl, indolinyl, isochromanyl, isoindolinyl, naphthyridinyl, phthalazinyl, piperonyl, purinyl, pyridopyridyl, quinazolinyl, tetrahydroquinolinyl, thienofuryl, thienopyridyl, thienothienyl, and the like.
Exemplary substituents for the terms xe2x80x9cheterocycle,xe2x80x9d xe2x80x9cheterocyclic,xe2x80x9d and xe2x80x9cheterocycloxe2x80x9d include one or more substituent groups as described above for substituted alkyl or substituted aryl, and smaller heterocyclos, such as, epoxides, aziridines and the like.
The term xe2x80x9calkanoylxe2x80x9d refers to xe2x80x94C(O)-alkyl.
The term xe2x80x9csubstituted alkanoylxe2x80x9d refers to xe2x80x94C(O)-substituted alkyl.
The term xe2x80x9cheteroatomsxe2x80x9d shall include oxygen, sulfur and nitrogen.
The compounds represented by formulas I, II, III, IV above may exist as multiple optical, geometric, and stereoisomers. While the compounds shown herein are depicted for one optical orientation, included within the present invention are all isomers and mixtures thereof.
Use and Utility
The compounds represented by formulas III and IV above are microtubule-stabilizing agents. The compounds, and thus the process, are useful in the treatment of a variety of cancers and other proliferative diseases including, but not limited to, the following:
carcinoma, including that of the bladder, breast, colon, kidney, liver, lung, ovary, pancreas, stomach, cervix, thyroid and skin, including squamous cell carcinoma;
hematopoietic tumors of lymphoid lineage, including leukemia, acute lymphocytic leukemia, acute lymphoblastic leukemia, B-cell lymphoma, T-cell lymphoma, Hodgkins lymphoma, non-Hodgkins lymphoma, hairy cell lymphoma and Burketts lymphoma;
hematopoietic tumors of myeloid lineage, including acute and chronic myelogenous leukemias and promyelocytic leukemia;
tumors of mesenchymal origin, including fibrosarcoma and rhabdomyoscarcoma;
other tumors, including melanoma, seminoma, teratocarcinoma, neuroblastoma and glioma;
tumors of the central and peripheral nervous system, including astrocytoma, neuroblastoma, glioma, and schwannomas;
tumors of mesenchymal origin, including fibrosarcoma, rhabdomyoscaroma, and osteosarcoma; and
other tumors, including melanoma, xeroderma pigmentosum, keratoacanthoma, seminoma, thyroid follicular cancer and teratocarcinoma.
The compounds represented by formulas III and IV above will also inhibit angiogenesis, thereby affecting the growth of tumors and providing treatment of tumors and tumor-related disorders. Such anti-angiogenesis properties of the compounds represented by formulas III and IV will also be useful in the treatment of other conditions responsive to anti-angiogenesis agents including, but not limited to, certain forms of blindness related to retinal vascularization, arthritis, especially inflammatory arthritis, multiple sclerosis, restinosis and psoriasis.
Compounds represented by formulas III and IV will induce or inhibit apoptosis, a physiological cell death process critical for normal development and homeostasis. Alterations of apoptotic pathways contribute to the pathogenesis of a variety of human diseases. Compounds represented by formulas III and IV, as modulators of apoptosis, will be useful in the treatment of a variety of human diseases with aberrations in apoptosis including, but not limited to cancer, particularly but not limited to, follicular lymphomas, carcinomas with p53 mutations, hormone dependent tumors of the breast, prostrate and ovary, and precancerous lesions such as familial adenomatous polyposis, viral infections including but not limited to herpesvirus, poxvirus, Epstein-Barr virus, Sindbis virus and adenovirus, autoimmune diseases such as systemic lupus erythematosus, immune mediated glomerulonephritis, rheumatoid arthritis, psoriasis, inflammatory bowel diseases and autoimmune diabetes mellitus; neurodegenerative disorders such as Alzheimer""s disease, AIDS-related dementia, Parkinson""s disease, amyotrophic lateral sclerosis, retinitis pigmentosa, spinal muscular atrophy and cerebellar degeneration; AIDS; myelodysplastic syndromes; aplastic anemia; ischemic injury associated myocardial infarctions; stroke and reperfusion injury; restenosis; arrhythmia; atherosclerosis; toxin-induced or alcohol induced liver diseases; hematological diseases such as chronic anemia and aplastic anemia; degenerative diseases of the musculoskeletal system such as osteoporosis and arthritis; aspirin-sensitive rhinosinusitis; cystic fibrosis; multiple sclerosis; kidney diseases; and cancer pain.
The compounds represented by formulas III and IV are also useful in combination with known anti-cancer and cytotoxic agents and treatments, including radiation. If formulated as a fixed dose, such combination products employ the compounds represented by formulas III and IV within the dosage range described below and the other pharmaceutically active agent within its approved dosage range. Compounds represented by formulas III and IV can be used sequentially with known anticancer or cytotoxic agents and treatment, including radiation when a combination formulation is inappropriate. Especially useful are cytotoxic drug combinations wherein the second drug chosen acts in a different phase of the cell cycle, e.g. S phase, than the present compounds represented by formulas III and IV which exert their effects at the G2-M phase.
The compounds prepared in accordance with the present invention can be formulated with a pharmaceutical vehicle or diluent for oral, intravenous or subcutaneous administration. Such pharmaceutical compositions can be formulated in a classical manner well known to those of ordinary skill in the art using solid or liquid vehicles, diluents and additives appropriate to the desired mode of administration. Orally, the compounds can be administered in the form of tablets, capsules, granules, powders and the like. The compounds are administered in a dosage range of about 0.05 to 200 mg/kg/day, preferably less than 100 mg/kg/day, in a single dose or in 2 to 4 divided doses.
Methods of Preparation
The intermediate compounds represented by formulas I and II are prepared from epothilone compounds represented by formula V in Scheme 1, particularly epothilone C or D wherein R1 is as defined above. The epothilone starting materials will fall under the general formulas III and IV as shown above. The advantage of the subject process is that it can be utilized to transform epothilone compounds that may have less than optimum properties into other analogs that have more desirable properties. The epothilone starting materials represented by formula V and formula XV are known compounds. See, for example, Kim et al., Org. Lett., 2, 1537 (2000); Hofle et al., Angew. Chem. Int. Ed. Engl., 35, 1567-1569 (1996); WO 93/10121 published May 27, 1993; and WO 97/19086 published May 29, 1997; Nicolaou et al., Angew Chem. Int. Ed. Engl., 36, 2097-2103 (1997); and Su et al., Angew Chem. Int. Ed. Engl., 36, 2093-2097 (1997).
As illustrated in Scheme 1, the epothilone starting material V is treated with a suitable enzyme that causes the molecule to degrade to yield a compound represented by formula VI as illustrated in Scheme 1. Suitable enzymes include, without intended limitation, pig liver esterase, chymotrypsin, or pancreatin. The carboxyl moiety of the compound represented by formula VI is then esterified to form an ester represented by formula VII by treatment with an alkylating agent such as diazomethane, trimethylsilyl diazomethane, or an alkyl halide. In the reaction illustrated in Scheme 1, trimethylsilyldiazomethane is utilized as the alkylating agent to form the methyl ester of the carboxyl moiety.
The ester compounds represented by formula VII are then treated to form protecting groups, such as silanes, on the hydroxyl groups. This is carried out by reaction with suitable agents such as trialkylsilyl halides, triflates, i.e. trifluoromethane sulfonates, to form a compound represented by formula VIII wherein P1, P2 and/or P3 are as defined above. A preferred reagent for forming the protecting groups on the hydroxyls is t-butyldimethylsilyl trifluoromethanesulfonate. The compounds represented by formula VIII are then oxidized, e.g. by ozone, to cleave the olefin at position 12, thereby forming the subject intermediate compounds represented by formula I.
The intermediate compounds of the present invention represented by formula I are suitably converted to the subject intermediate compounds represented by formula II in two steps as shown in Scheme 1. In the first step, the compound represented by formula I is reacted with a suitable Wittig type reagent represented by the following formula 
wherein R2 and P3 are as defined above, illustrated by formula IX in Scheme 1. The reagents represented by formula IX can be prepared, for example, as described by Nicolaou et al., Angew. Chem., Vol. 110, No. 85 (1998). The reaction of the compound represented by formula IX and the compound represented by formula I in Scheme 1 is an ester represented by formula X in Scheme 1. The ester moiety at position 1 of the compounds represented by formula X is then hydrolyzed by methods well know in the art, e.g. treatment with a suitable base, such as aqueous hydroxides or carbonates, to yield the carboxylic acids represented by formula II. 
Compounds of formula II and methods for synthesizing epothilone analogs from such compounds are known. See, Nicolaou et al., J. Amer. Chem. Soc., 119, 7974 (1997). The protected hydroxyl groups of compounds of formula II may be deprotected according to several known procedures. See, Greene and Wuts, xe2x80x9cProtective Groups In Organic Synthesis,xe2x80x9d 2nd Ed., John Wiley and Sons, Inc., New York, 1991.
Intermediate compound represented by formula I can also be prepared according to the procedures depicted in Scheme 2. 
As illustrated in Scheme 2, the epothilone starting material XV is treated with a suitable enzyme that cleaves the compound of formula XV to form a compound of formula XVI bearing a carboxyl group. Suitable enzymes include, but are not limited to, pig liver esterase, chymotrypsin or pancreatin. The carboxyl group of compound XVI is then esterified with an alkylating agent to form the ester compound XVII. Examples of alkylating agents include, but are not limited to, diazomethane, trimethylsilyl diazomethane or an alkyl halide. As an example, in the reaction depicted in Scheme 2, diazomethane is used as the alkylating agent. The ester compound XVII is next hydrolyzed to form a diol compound of formula XVIII. This hydrolysis step is performed under acidic conditions. Finally, compound XVIII is oxidized to form the intermediate of formula I. An example of an oxidizing agent is sodium periodate. Other examples include, but are not limited to, Ca(OCl)2, NaBiO3, I(OAc)3, HIO4, Amberlite and 904-NaIO4 (J. Chem. Soc. Perkin I, 509 (1982)), Pb(OAc)2, HgO and I2, MnO2, KmnO4, H2CrO4, PCC (Syn. Commun., 12, 833 (1982)), RuCl2 (PPh3)3 and BaMnO4.
The compounds represented by formulas I and II are useful as intermediates in the preparation of epothilone analogs characterized by enhanced activity.
All references cited herein are incorporated by reference as if set forth at length herein.
The following non-limiting examples serve to illustrate the practice of the invention.